Research reveals that 80 per cent of staff in their first seven years in the classroom produced value-added results at or above the expected level. But this fell to 68 per cent for those with between eight and 23 years’ experience and to 59 per cent for those with 24 years or more

Professor Christopher Day, who led the study, said: “This was a surprise to us. Until now it was thought that when you enter teaching you are a novice and you move through stages until you become an expert.